Footwear bottom with anti-shock insert

ABSTRACT

The present invention relates to a moulded footwear bottom, which incorporates one or more rigid protuberances ( 4, 5 ) that protrude from the upper surface and are engaged inside at least one shock-absorbing insert ( 2   a,    2   b ) provided with corresponding slots ( 3, 6 ) designed to house the said rigid protuberances ( 4, 5 ).

The present patent application relates to a moulded footwear bottom provided with a special anti-shock insert.

Footwear bottoms moulded from plastic materials are traditionally provided with anti-shock inserts, that is to say a sort of shock-absorbing cushions mounted on the heel and designed to soften the repeated impacts with the ground suffered by the heel at every step.

The said anti-shock inserts are produced according to a standardised process.

In particular, an insert made of soft plastic material or a sort of air-filled cushion is incorporated in the material used to mould the bottom; in these cases, the insert or shock-absorbing cushion has a closed geometrical shape (circular, elliptical, square, etc.) and is drowned in the sole.

The said inserts maintain their shock-absorbing function until they do not lose their elastic properties, which tend to attenuate over time according to the extent of the elastic deformation suffered at every stress. The pressure discharged on the said inserts is directly proportional to the weight of the user and can vary by several tens of kilograms with the same foot size.

This means that the same model of ant-shock insert mounted on the same type and size of shoe can have a longer or shorter operating life according to the user.

In the case of inserts formed of air cushions, a problem is represented by the air-tightness and mechanical resistance of the perimeter welding line, since the said cushions are normally obtained by welding the edges of two semi-shells of soft, flexible material.

Also in this case, a different weight of the user corresponds to a different compression of the air contained in the cushion, with consequent mechanical stress that tends to detach the welded edges.

In view of the above, the said edges must be welded according to heavy duty conditions that, although not frequent, require a higher and therefore more expensive quality standard for the entire production.

The same is true for inserts obtained from a pad of thermoplastic rubber or other materials that are elastically deformed under pressure, whose elastic characteristics are normally improved both in terms of efficacy and duration by means of expensive additives.

In other words, a reduction of the maximum deformation of the anti-shock insert during its operating life would correspond to a reduction of production costs, selecting more economically convenient production techniques to guarantee a predefined reduced reliability.

The purpose of the present invention is to devise a footwear bottom moulded from plastic materials provided with an anti-shock insert, whose elastic deformation does not exceed a predetermined threshold value, regardless of the users weight.

This objective has been reached by the bottom of the invention, which incorporates one or more rigid protuberances that protrude from its upper surface and are engaged inside the said shock-absorbing insert, which is provided with suitable slots that house the said protuberances, being incapable of being elastically deformed under pressure.

The height of the said protuberances must be lower than the thickness of the anti-shock insert, in such a way that the insert can be elastically lowered under the weight of the foot, until the weight is discharged on the said protuberances, which act as supports thanks to their rigidity, thus preventing the additional elastic deformation of the shock-absorbing insert.

According to the preferred embodiment, the shock-absorbing insert is composed of an annular air cushion, with suitable shape and dimensions to be mounted in the heel, under the heel of the foot.

The bottom is provided with a space that can exactly house the said cushion, being inserted externally on a rigid pin that protrudes from the centre of the heel, having a height lower than the thickness of the cushion.

For purposes of clarity the description of the invention continues with reference to the enclosed drawing, which is intended for purposes of illustration only and not in a limiting sense, whereby:

FIG. 1 is an axonometric view of the bottom of the invention;

FIG. 2 is a section with a transversal plane of the bottom of the invention on the heel;

FIG. 3 is a section of FIG. 1 with the transversal plane III-III.

With reference to the enclosed figures, the bottom (1) of the invention is moulded from a single piece of plastic material, either rubber or thermoplastic material, in which a back space (1 a) and a front space (1 b) are obtained during moulding to house corresponding shock-absorbing inserts that may consist, according to the specific case, in air cushions or pads of soft, elastically deformed material, such as thermoplastic rubber, vulcanised rubber, PVC or polyurethane. In the embodiment illustrated in the enclosed figures, the shock-absorbing inserts consist in a first rear air cushion (2 a) and a second front air cushion (2 b).

The first air cushion (2 a) has an annular shape and suitable dimensions to be exactly housed in the said rear space (1 a) of the bottom (1). A rigid “pin” (4) is inserted in the hole (3) in the centre of the cushion (2 a), which protrudes from the bottom wall of the space (1 a), with height lower than the thickness of the air cushion (2 a), as shown in FIG. 2. The second front air cushion (2 b) is shaped as a tongue and is exactly housed in the front space (1 b) on the half sole of the bottom (1), which is provided with a series of protuberances (5) obtained during moulding and shaped as rigid segments, that are exactly housed inside corresponding slots (6) provided on the second front air cushion (2 b). Also in this case, the height of the protuberances (5) is lower than the thickness of the air cushion (2 b), as shown in FIG. 3. 

1. Footwear bottom moulded from plastic materials, of the type moulded from a single piece of suitable material, which is provided with a rear space (1 a) and/or a front space (1 b) housing corresponding shock-absorbing inserts (2 a and 2 b) that are elastically deformed under pressure, characterised in that at least one of these spaces (1 a, 1 b) is provided with one or more rigid protuberances (4, 5) engaged inside corresponding slots (3, 6) of the shock-absorbing inserts (2 a, 2 b) with thickness higher than the height of the said rigid protuberances (4, 5).
 2. Footwear bottom of claim 1, characterised in that the rear insert (2 a) has an annular shape and a central hole (3) in which a rigid “pin” (4) is inserted, protruding from the bottom wall of the rear space (1 a), having a height lower than the thickness of the insert (2 a).
 3. Footwear bottom of claim 1, characterised in that the front insert (2 b) is shaped as a tongue and is exactly housed in the front space (1 b) on the half sole of the bottom (1), which is provided with a series of protuberances (5) obtained during moulding and shaped as rigid segments, that are exactly housed inside corresponding slots (6) provided on the front insert (2 b) with thickness higher than the height of the rigid protuberances (5).
 4. Footwear bottom of claim 1, characterised in that the said shock-absorbing inserts (2 a, 2 b) consist in air-filled cushions.
 5. Footwear bottom of claim 1, characterised in that the shock-absorbing inserts (2 a, 2 b) consist in soft pads moulded from materials that are elastically deformed under pressure. 